The production of combination yarns comprising a core of continuous filament and a sheath of staple fibers is well known. The disadvantage of the known production processes is that their relatively low production rates make them uneconomical.
In commonly assigned U.S. application Ser. No. 959,190, filed Nov. 8, 1978, now U.S. Pat. No. 4,202,162, issued May 13, 1980, there was proposed a process for spinning textile fibers whereby the fibers are delivered to a perforated collecting surface having a limited suction zone in a current of air moving virtually at right angles to the surfaces of two friction discs. From the suction zone the fibers are passed at right angles to the direction of the air current into the gap between the narrowly spaced counter-rotating friction discs, such that the opposing faces impart a twist to the stable fiber.
Suprisingly, it has now been found that this general process is eminently adaptable to the production of combination yarns comprising a core of continuous filament and a sheath of staple fibers.
Accordingly, the instant invention is directed to a process for producing a combination yarn by the previously mentioned working procedure, featuring the marriage of a continuous filament with the staple fibers in the suction zone and the twisting of both components in the gap between the friction discs.
A basic advantage of the process according to the instant invention is that, when compared with known processes, it achieves essentially higher production rates and therefore increased efficiency. Furthermore, it improves the sheathing of the continuous filament with the staple fibers. The fact that true twist is not imparted to the continuous filament at the twisting stage, but only false twist, implies that the continuous filament is always located at the center of the combination yarn.
When continuous filaments of synthetic thermo-plastic material are employed, the false twist may be heat-set before being united with the staple fibers, whereby the continuous filament is permanently textured, thereby imparting elasticity to the combination yarn.
The process of the invention will be described in detail in conjunction with the appended drawings, which are schematic representations of the process and the apparatus used therein.